System and method for determining the position of a remote object

ABSTRACT

The invention provides methods and systems for determining the position of a remote object such as an in vivo medical device such as capsule or probe within a medical patient. The systems and methods of the invention may also be used in other enclosed environments such as fluid handling or mechanical systems. The systems and methods of the invention use one or more external magnetic sensor arrays for sensing the magnetic field of a remote object within a target area. The position of the object is determined by applying magnetic field spatial geometry characterization point analysis to evaluate the sensed magnetic field.

TECHNICAL FIELD

The invention relates to the use of magnetic fields for determining theposition of remote objects. More particularly, the invention relates tosystems and methods for determining the position of a remote objecthaving a magnetic field by using magnetic field spatial geometrycharacterization point analysis derived from externally sensed magneticfield data.

BACKGROUND OF THE INVENTION

Ingestible wireless medical capsules are known in the medical arts. Suchcapsules telemetrically transmit information to a receiving andrecording apparatus located outside the body. The wireless capsule isswallowed and travels through the digestive tract, collecting andtransmitting data during the course of its journey. Receiving andrecording apparatus is stationed external to the body. In general, aftera day or two, the disposable capsule is excreted naturally from the bodyand the recorded data, such as for example, temperature, pH, pressure,and transit time, may be transferred for analysis and/or storage. It isknown in the art to use wireless medical capsules for collecting imagesby equipping them with cameras, or for delivering doses of medication togeneral areas of the digestive system by equipping them with drugreservoirs.

The deployment and detection of relatively small probes or sensors forreconnaissance in confined, inaccessible, or remote spaces is useful inmany contexts. Determining the position of an object during deploymentfaces may challenges. In many applications, the target environment maybe no more than a few liters in volume. It is sometimes desirable todetermine the position of an abject, such as a probe or sensor capsule.with as much precision as possible. Remote sensing may be used in manyendeavors, such as industrial or medical applications. For example, thecurrently available wireless capsules used in the medical field arecarried by peristalsis through the digestive tract, and the capsulelocation during the journey is either unknown or only approximatelyknown. Similarly, in non-medical applications, a probe capsule may becarried by fluid flow and/or gravity, through a system of piping ortubing for example, and its position at any given time onlyapproximated. The lack of position information is a drawback of currentwireless capsule technology. For example, often a doctor reviewing datafrom an in vivo capsule does not know the precise location of featuresindicated by the data, e.g., an image of a gastro-intestinal tumor.Often an additional scoping procedure or even surgery may be required inorder to determine the exact location of the problem. In connection withmedical devices, some development of magnetic locating techniques hasoccurred. One approach, exemplified by U.S. Pat. No. 5,558,091 to Acker,is to embed a magnetic sensor in an in vivo capsule, and track thesensor within the body by relating it to magnetic fields external to thebody. Although this approach may be useful to some degree, it does nottake into account the effect of the earth's magnetic field or thepotential interference of additional magnetic fields such as those whichmay emanate from electrical current and ferromagnetic materials nearby.Another approach, exemplified by U.S. Pat. No. 6,216,028 to Haynor, isto place a magnet on a medical device such as the tip of a probeinserted into the patient, and detect the magnet's field distributionwith sensors located on an outside surface of the body. This approachproposes using four magnetic sensors to measure the magnetic field inthe x, y, and z axes, and modeling the magnetic tip as a dipole, solvinga number of nonlinear equations to determine the position of themagnetic dipole. The complexity of the computations involved requireconsiderable computing power and/or a significant amount of time tocomplete. The complexity of this approach also increases the potentialfor considerable error.

Improved systems and methods for accurately determining the position ofa remote object, such as a locatable wireless capsule or probe would beuseful and advantageous in order to accurately match a location withremotely detected images or other parameters such as pH, temperature,pressure values and so forth. It may also provide advantages foraccurately guiding the delivery of medications, or for taking biopsies,or for later surgery. In non-medical applications, it may be used forinspecting piping or fluid-handling systems. Used in conjunction withcapsules or probes capable of controlled movement, the capability fortimely detection of the probe or capsule position would be particularlyadvantageous. Due to the foregoing and other problems and potentialadvantages, improved position determining methods and systems usingmagnetic fields would a useful contribution to the applicable arts.

SUMMARY OF THE INVENTION

In carrying out the principles of the present invention, in accordancewith preferred embodiments, the invention provides advances in the artswith novel methods and apparatus directed to detecting and determiningthe position of a remote object, such as a capsule or probe, deployedwithin a target area by sensing its magnetic field in one or moreplanes. The invention may be used with objects, including but notlimited to capsules and probes interchangeably, provided that thetracked object includes a permanent or electrical magnet. Thus, theterms capsule and probe are used interchangeably herein unless noted.

According to one aspect of the invention, a system for determining theposition of a remote object includes a targeted object including its ownmagnetic field for placement on site, i.e., in situ. The system alsoincludes an external magnetic sensor array configured for sensing themagnetic field of the object, e.g., capsule or probe for example, in oneor more planes. Computing apparatus is used for magnetic field spatialgeometry characterization point analysis in order to determine theposition of the object from the sensed magnetic field.

According to another aspect of the invention, a system for determiningthe position of a remote object as exemplified in the above embodimentalso includes at least one background offset sensor for correctingposition data for locally measured magnetic fields.

According to another aspect of the invention, a system for determiningthe position of a remote object as described herein further includes atleast one non-stationary sensor plane.

According to yet another aspect of the invention, an in vivo positiondetermining system for medical use includes a capsule or probe having amagnetic field for placement in vivo. The system also includes, deployedoutside the body, an external magnetic sensor array configured forsensing the magnetic field of the capsule in one or more planes, as wellas magnetic field spatial geometry characterization point analysisapparatus for determining the position of the capsule in vivo from thesensed magnetic field.

According to another aspect of the invention, a preferred embodiment ofa method for determining the position of a remote object includes stepsfor positioning an external magnetic sensor array for sensing themagnetic field of an object within a target area, and using the sensedmagnetic field of the object, determining object position data usingmagnetic field spatial geometry characterization point analysis.

According to another aspect of the invention, an in vivo positiondetermination method includes the step of placing a capsule comprising amagnetic field within a patient, or in vivo. In further steps, anexternal magnetic sensor array is located for sensing the magnetic fieldof the capsule. Using the sensed magnetic field, capsule position datais computed by magnetic field spatial geometry characterization pointanalysis.

The invention has advantages including but not limited to providing oneor more of the following; computationally efficient remote positioncalculation, improved positioning accuracy, and relatively rapidposition determination. These and other advantageous, features, andbenefits of the invention can be understood by one of ordinary skill inthe arts upon careful consideration of the detailed description ofrepresentative embodiments of the invention in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from considerationof the description and drawings in which:

FIG. 1 is a conceptual block diagram providing an overview of systemsand methods for determining the position of a remote capsule;

FIG. 2 depicts an example of a preferred embodiment of a positiondetermination system and method in which four magnetic field sensorplanes are used;

FIG. 3 illustrates an example of an alternative preferred embodiment ofa position determination system and method in which two magnetic fieldsensor planes are used;

FIG. 4 provides an example of an alternative preferred embodiment of aposition determination system and method in which a single magneticfield sensor plane is used; and

FIGS. 5A and 5B show an example of an additional alternative preferredembodiment of a position determination system and method in which asingle magnetic field sensor plane is employed.

References in the detailed description correspond to like references inthe various drawings unless otherwise noted. Descriptive and directionalterms used in the written description such as front, back, top, bottom,upper, side, et cetera, refer to the drawings themselves as laid out onthe paper and not to physical limitations of the invention unlessspecifically noted. The drawings are not to scale, and some features ofembodiments shown and discussed are simplified or amplified forillustrating principles and features as well as advantages of theinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

While the making and using of various exemplary embodiments of theinvention are discussed herein, it should be appreciated that thesystems and methods exemplify inventive concepts which can be embodiedin a wide variety of specific contexts. It should be understood that theinvention may be practiced in various applications and embodimentswithout altering the principles of the invention. For purposes ofclarity, detailed descriptions of functions, components, and systemsfamiliar to those skilled in the applicable arts are not included. Ingeneral, the invention provides systems and methods for determining theposition of a remote object, for example, an encapsulated probe such asan in vivo medical device, or a probe deployed within a fluid-handlingsystem of piping or tubing. The invention is described in the context ofrepresentative example embodiments. Although variations on the detailsof the embodiments are possible, each has advantages over the prior artdue at least in part to increased efficiency realized by performingfewer and/or less complex computations.

An exemplary embodiment of a system and method for remotely determiningthe position of an object is shown in the conceptual view of FIG. 1. Anoperating environment 10 (not part of the invention), such as a medicalpatient or a confined area such as a mechanical, fluid-handling, orhydraulic system, and at least one sensor array 12 are positionedrelative to one another in a configuration further described herein. Thesensor array(s) 12 include one or more individual sensor cells 14,preferably uniformly distributed in a sensor plane corresponding with atarget area 16 of the operating environment 10. A suitable computer ordata processing apparatus 18 is operably coupled to the sensor arrays 12for performing computations referenced and described herein. A capsule20, or probe, is preferably deployed inside the target area 16. In thecase of a medical implementation, the device may be swallowed by a humanor inserted into a veterinary patient, for example. In otherimplementations, the capsule may be introduced into a system of pipes, atank or other vessel, mechanical enclosure, or other confined orinhospitable environment where remote sensing or probing is desirable.The capsule 20 includes a dipole magnetic field, preferably generated bya permanent magnet included as a part of the capsule, represented by thediagram inset, and further described by Equation 1. The dipole magneticfield B, is a scalar value (not a vector) wherein m represents themagnetic moment of the magnetic dipole (for the purposes of thisdescription, capsule 20), and wherein r represents distance from themagnetic dipole 20. Angle θ represents the orientation of the capsule 20relative to moment and distance. It should be appreciated that thecapsule 20 typically also includes devices for gathering one or moredata points from its surroundings, such as temperature, pH, pressure,chemistry, charge, imagery, and so forth.

$\begin{matrix}{{B\left( {r,\theta} \right)} = {\frac{\mu_{0}m}{4\; \pi \; r^{3}}\sqrt{1 + {3\; \cos^{2}\theta}}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

Examples of magnetic field sensor cells 14 include Hall effect sensors,which vary their output voltage responsive to changes in magnetic field,and magneto resistive sensors, which vary their electrical resistance inresponse to an external magnetic field. The Hall sensor is capable of agreater detection range, whereas magneto resistive sensors are capableof greater sensitivity. Other magnetic sensor types or combinations ofsensors may also be used without departure from the invention. A sensorarray 12, as shown in the example of FIG. 1, preferably includesmultiple sensors in a planar arrangement. Suitable field magneticsensors on the order of 2 mm×2 mm are commercially available and arepresently preferred for in vivo system embodiments. For example, in anarray of 2 mm magnetic filed sensors spaced 5 mm apart, when thedetected magnetic field is 0.01 Gauss, using the systems and methodsfurther described herein, a spatial resolution of 0.5 mm is attainable.Accordingly, the position of the magnetic field, e.g., magnetic dipoleor capsule 20 location, may be determined within about 1 mm. In order toscan a target area larger than the sensor array, and/or to reduce thenumber of sensor cells required in an array, the sensor array may bemoved relative to the target area, or vice versa. The magnetic sensorarray and/or target area movement is preferably conducted along theplane described by the sensor array, preferably using a mechanical guideto ensure that the correct orientation is maintained and automated orhuman impelling force.

Preferably, positioning accuracy is enhanced by taking into account anoffset magnetic field value when performing positioning computationsdescribed herein. A value for the earth's magnetic field, for example,may be stored and applied for correction of calculations made based onmagnetic field sensor values indicative of the position of the capsule.Additionally, or alternatively, a magnetic field offset sensor 24 may beused to provide an actual offset value for the particular location andconditions, e.g. the earth magnetic field and the presence of magneticmaterials or field-generating electric current. The capsule positiondata is preferably corrected using the magnetic field offset data. Themagnetic field offset sensor 24 is preferably positioned so that it willnot sense the magnetic field of the capsule 20, and bears a known,preferably constant, spatial relationship to the magnetic field sensorcells 14 of the magnetic field sensor array 12.

Now referring primarily to FIG. 2, a preferred embodiment of a systemand method is shown, in which a target area 16 is encompassed withinfour magnetic field sensor planes, denominated 22A, 22B, 22C, and 22D.Preferably, the sensor planes are configured in sets of two parallelplanes. As shown in FIG. 2, front plane 22A is parallel to back plane22B, and left plane 22C is parallel to right plane 22D. Preferably, themaximum magnetic field point is determined by magnetic field sensorreadings on each plane, indicated in FIG. 2 by points A, B, C, and D,respectively. The maximum points on the opposing planes are used todefine lines AB and CD. The intersection of the lines indicates thepoint O within the target area 16 at which the magnetic field isstrongest, thus giving the capsule 20 position in three-dimensionalspace. Preferably, a magnetic field offset is applied to correct theposition information based on what is known about magnetic fieldspresent in the operating environment, such as the earth's magnetic fieldand/or additional locally detected magnetic fields. Those skilled in thearts should note that this particular embodiment does not require dataconcerning the magnetic field direction; no magnetic moment value isneeded. The method and system described in this embodiment offersadvantages in efficiency, requiring reduced computation and processingtime, and/or reduced complexity relative to the prior art.

In another preferred embodiment, illustrated in FIG. 3, the position ofthe capsule 20 may be determined using two sensor planes, denoted 32Aand 32B. The sensor planes 32A, 32B, are preferably parallel. Themaximum magnetic field points, A, B, and the magnetic field vector areused to determine the dipole location O and orientation. Referring toEquations 2-7, the moment of the magnetic dipole is related to themagnetic field. The dipole magnetic moment m is derived from the dipolemoment along line AB and perpendicular to line AB. (Equations 1-2). Themagnetic field at point A can be derived from the magnetic field alongline AB, and perpendicular to line AB. The same can be done for point B.The magnetic fields of the dipole are preferably computed as shown inEquations 3 and 4. Since the magnetic fields along the x, y, and z axesare measured at the magnetic field sensor cells, the line ABperpendicular and parallel component values can be calculated with themeasurement data. Thus the dipole position, point O, can be calculated(Equation 5), and the angle θ can be derived. (Equation 6). The dipole'sperpendicular orientation is the same as the line AB perpendicularmagnetic field component, thus the dipole orientation can also bedetermined. It should be noted that the two parallel planes mayalternatively be located on the same side of the dipole withoutdeparture from the invention, since the line between their maximumpoints, e.g., line AB, would nevertheless be established.

$\begin{matrix}{\overset{\rightarrow}{m} = {{\overset{\rightarrow}{m}}_{{AB}\;//} + {\overset{\rightarrow}{m}}_{{AB}\bot}}} & \left( {{Eq}.\mspace{14mu} 2} \right) \\{{m_{{AB}\;//} = {m\; \cos \; \theta}},{m_{{AB}\;\bot} = {m\; \sin \; \theta}}} & \left( {{Eq}.\mspace{14mu} 3} \right) \\{{B_{{A\_ {AB}}\;//} = \frac{\mu_{0}m_{{AB}\;//}}{2\; \pi \; r_{OA}^{3}}},{B_{{B\_ {AB}}\;//} = \frac{\mu_{0}m_{{AB}\;//}}{2\; \pi \; r_{OB}^{3}}}} & \left( {{Eq}.\mspace{14mu} 4} \right) \\{{B_{{A\_ {AB}}\;\bot} = \frac{\mu_{0}m_{{AB}\;\bot}}{4\; \pi \; r_{OA}^{3}}},{B_{{B\_ {AB}}\;\bot} = \frac{\mu_{0}m_{{AB}\;\bot}}{4\; \pi \; r_{OB}^{3}}}} & \left( {{Eq}.\mspace{14mu} 5} \right) \\{\frac{OA}{OB} = {\sqrt[3]{\frac{B_{{A\_ {AB}}\;//}}{B_{{B\_ {AB}}\;//}}} = \sqrt[3]{\frac{B_{{A\_ {AB}}\;\bot}}{B_{{B\_ {AB}}\;\bot}}}}} & \left( {{Eq}.\mspace{14mu} 6} \right) \\{{\tan \; \theta} = {\frac{B_{{A\_ {AB}}\;\bot}}{2\; B_{{A\_ {AB}}\;//}} = \frac{B_{{B\_ {AB}}\;\bot}}{2\; B_{{B\_ {AB}}\;//}}}} & \left( {{Eq}.\mspace{14mu} 7} \right)\end{matrix}$

In an example of an alternative embodiment of the invention, depicted inFIG. 4, a single magnetic field sensor plane 42 is used to determine theposition of the magnetic field of a capsule 20. By the partialdifferentiation of the magnetic field curve, the maximum field conditionis derived. The set of the nonlinear equations, Equations 8-11.6,express the derivation of the dipole location and orientation from thesensed magnetic field.

$\begin{matrix}{{{B\left( {x,y,z} \right)} = {\sqrt{B_{x}^{2} + B_{y}^{2} + B_{z}^{2}} = {\frac{\mu_{0}}{{4\; \pi}\;}\frac{1}{r^{4}}\sqrt{{3\; Q^{2}} + {m^{2}r^{2}}}}}}{Q = \left\lbrack {{m_{x}\left( {x - x_{0}} \right)} + {m_{y}\left( {y - y_{0}} \right)} + {m_{z}\left( {z - z_{0}} \right)}} \right\rbrack}{r = \sqrt{\left( {x - x_{0}} \right)^{2} + \left( {y - y_{0}} \right)^{2} + \left( {z - z_{0}} \right)^{2}}}} & \left( {{Eq}.\mspace{14mu} 8} \right) \\{{F\left( {x,y,z} \right)} = {{\frac{\mu_{0}}{{4\; \pi}\;}\frac{1}{r^{4}}\sqrt{{3\; Q^{2}} + {m^{2}r^{2}}}} - B}} & \left( {{Eq}.\mspace{14mu} 9} \right) \\\left( {\frac{\partial F}{\partial x},\frac{\partial F}{\partial y},\frac{\partial F}{\partial z}} \right) & \left( {{Eq}.\mspace{14mu} 10} \right) \\{{\frac{\partial F}{\partial x} = 0},} & \left( {{Eq}.\mspace{14mu} 11.1} \right) \\{{\frac{\partial F}{\partial y} = 0},} & \left( {{Eq}.\mspace{14mu} 11.2} \right) \\{\frac{\partial F}{\partial z} = 1} & \left( {{Eq}.\mspace{14mu} 11.3} \right) \\{B_{x} = {\frac{\mu_{0}}{{4\; \pi}\;}\frac{{3\; {Q\left( {x - x_{0}} \right)}} - {m_{x}r^{2}}}{r^{5}}}} & \left( {{Eq}.\mspace{14mu} 11.4} \right) \\{B_{y} = {\frac{\mu_{0}}{{4\; \pi}\;}\frac{{3\; {Q\left( {y - y_{0}} \right)}} - {m_{y}r^{2}}}{r^{5}}}} & \left( {{Eq}.\mspace{14mu} 11.5} \right) \\{B_{z} = {\frac{\mu_{0}}{{4\; \pi}\;}\frac{{3\; {Q\left( {z - z_{0}} \right)}} - {m_{z}r^{2}}}{r^{5}}}} & \left( {{Eq}.\mspace{14mu} 11.6} \right)\end{matrix}$

Assuming for example, that the maximum magnetic field is at point A (0,0, 0). The equal magnetic field curve Q has a tangent plane (z=0) at A,and the normal line is vector (0, 0, 1). The magnetic field, B(x, y, z)is as shown by Equation 8. The curve Q equation is as represented byEquation 9. The vector of the curve surface is shown by Equation 10.Considering the normal line at the tangent plane at point A permits thederivation of six equations (Equations 11.1-11.6), which can be used tosolve for the six unknown parameters, denoted, x0, y0, z0, mx, my, andmz, that represent the magnetic dipole location O, in this casecoinciding with capsule 20, position and orientation.

In another example of an alternative embodiment of the invention,illustrated using FIGS. 5A and 5B, a single magnetic field sensor plane52 is used to determine the position of the magnetic field. In thismethod the magnetic moment is used to provide a simpler and fasterapproach for solving the nonlinear equation set (Equations 8-11.6). Itshould be appreciated that this approach may also be combined with theabove method, eliminating the requirement that the magnetic moment valuefirst be known.

$\begin{matrix}{{B\; {\cos \left( {\beta + \phi} \right)}} = {\frac{\mu_{0}}{{4\; \pi}\;}\frac{2\; m\; \cos \; \alpha}{r^{3}}}} & \left( {{Eq}.\mspace{14mu} 12.1} \right) \\{{B\; {\sin \left( {\beta + \phi} \right)}} = {\frac{\mu_{0}}{{4\; \pi}\;}\frac{m\; \sin \; \alpha}{r^{3}}}} & \left( {{Eq}.\mspace{14mu} 12.2} \right) \\{{{tg}\left( {\beta + \phi} \right)} = {2\; {tg}\; \alpha}} & \left( {{Eq}.\mspace{14mu} 12.3} \right) \\{{{tg}\left( {\beta + \alpha} \right)} = {2^{2/3}{tg}\; \alpha}} & \left( {{Eq}.\mspace{14mu} 12.4} \right)\end{matrix}$

Assuming for the sake of example that the magnetic dipole is at (0, 0,0) oriented along the z-axis; The normal line n is perpendicular to thetangent plane at the measured B maximum. By geometric symmetry, themaximum field vector B and the normal vector n, and the dipole momentvector m, are in the same plane. This effectively reduces the threedimensional positioning problem to a two dimensional problem. The angleφ between the B vector and n vector is known from sensor data. In orderto solve the problem, α and β are first determined. Evaluating themaximum magnetic field vector and dipole moment vector, shown along theconnecting dashed line in FIG. 5A, the relationships are calculatedusing Equations 12.1 and 12.2. The first angle equations are derived(Equations 12.3 and 12.4) in accordance with the topology change asshown in FIG. 5B. The space defined by the dashed line shown is a lineargeometry transform from the solid taken along the z direction. From thedipole field equation, transferring the z scale with about {square rootover (2)} the curve surface may be described as a sphere, but thetopology characteristics are maintained, such as the tangent points.Given the geometric relationships of the points, using Equations12.3-12.4, α and β can be found, determining the dipole orientation. Ifthe magnetic moment m is known, using Equation 8 or 9, the distance R isdetermined, representing the magnetic dipole location 20.Computationally, this method is simpler relative to alternatives,providing advantages in efficiency, particularly for makingtime-sensitive position determinations, such as, for example in systemsequipped for real-time sensing and/or controlled movement of a capsuleor probe.

The systems and methods of the invention provide one or more advantagesincluding but not limited to, providing accurate position determinationfor remote objects using measurements and analysis based on magneticfields, increased efficiency, reduced costs. While the invention hasbeen described with reference to certain illustrative embodiments, thosedescribed herein are not intended to be construed in a limiting sense.For example, variations or combinations of steps or materials in theembodiments shown and described may be used in particular cases withoutdeparture from the invention. Although the presently preferredembodiments are described herein in terms or planes and planar geometry,it is possible to practice the invention by substituting curved surfacesfor planes, and adapting the calculations based on the selectedcurvature. Also, the computations described in terms of maximum valuesmay be adapted to use minimum values or selected intermediate valueswithout departure from the principles of the invention. These and othermodifications and combinations of the illustrative embodiments as wellas other advantages and embodiments of the invention will be apparent topersons skilled in the arts upon reference to the drawings, description,and claims.

1. A system for determining the position of a remote capsule comprising:a capsule comprising a magnetic field for placement in situ; an externalmagnetic sensor array configured for sensing the magnetic field of thecapsule in one or more planes; and magnetic field spatial geometrycharacterization point analysis apparatus for determining the positionof the capsule from the sensed magnetic field.
 2. The system fordetermining the position of a remote capsule according to claim 1wherein the magnetic sensor array further comprises one magnetic fieldsensor plane.
 3. The system for determining the position of a remotecapsule according to claim 1 wherein the magnetic sensor array furthercomprises two magnetic field sensor planes.
 4. The system fordetermining the position of a remote capsule according to claim 1wherein the magnetic sensor array further comprises three magnetic fieldsensor planes.
 5. The system for determining the position of a remotecapsule according to claim 1 wherein the magnetic sensor array furthercomprises four magnetic field sensor planes.
 6. The system fordetermining the position of a remote capsule according to claim 1wherein the magnetic sensor array further comprises at least fivemagnetic field sensor planes.
 7. The system for determining the positionof a remote capsule according to claim 1 further comprising at least onebackground offset sensor.
 8. The system for determining the position ofa remote capsule according to claim 1 wherein the magnetic sensor arrayfurther comprises at least one non-stationary sensor plane.
 9. Thesystem for determining the position of a remote capsule according toclaim 1 wherein the magnetic sensor array further comprises at least oneHall sensor.
 10. The system for determining the position of a remotecapsule according to claim 1 wherein the magnetic sensor array furthercomprises at least one magneto resistive sensor.
 11. An in vivo positiondetermining system comprising: a capsule comprising a magnetic field forplacement in vivo; an external magnetic sensor array configured forsensing the magnetic field of the capsule in one or more planes; andmagnetic field spatial geometry characterization point analysisapparatus for determining the position of the capsule in vivo from thesensed magnetic field.
 12. The in vivo position determining systemaccording to claim 11 wherein the magnetic sensor array furthercomprises one magnetic field sensor plane.
 13. The in vivo positiondetermining system according to claim 11 wherein the magnetic sensorarray further comprises two magnetic field sensor planes.
 14. The invivo position determining system according to claim 11 wherein themagnetic sensor array further comprises three magnetic field sensorplanes.
 15. The in vivo position determining system according to claim11 wherein the magnetic sensor array further comprises four magneticfield sensor planes.
 16. The in vivo position determining systemaccording to claim 11 wherein the magnetic sensor array furthercomprises at least five magnetic field sensor planes.
 17. The in vivoposition determining system according to claim 11 wherein the magneticsensor array further comprises a background offset sensor.
 18. The invivo position determining system according to claim 11 wherein themagnetic sensor array further comprises at least one non-stationarysensor plane.
 19. The in vivo position determining system according toclaim 11 wherein the magnetic sensor array further comprises at leastone Hall sensor.
 20. The in vivo position determining system accordingto claim 11 wherein the magnetic sensor array further comprises at leastone magneto resistive sensor.
 21. A method for determining the positionof a remote object comprising the steps of: placing an external magneticsensor array for sensing the magnetic field of an object within a targetarea; and using the sensed magnetic field of the object, determiningobject position data using magnetic field spatial geometrycharacterization point analysis.
 22. The method according to claim 21comprising the further steps of; using a magnetic offset sensor forsensing background magnetic field presence; offsetting the objectposition data using the sensed background magnetic field.
 23. The methodaccording to claim 21 comprising the further steps of; placing anexternal magnetic offset sensor for sensing background magnetic fieldpresence; offsetting the capsule position data using the sensedbackground magnetic field.
 24. The method according to claim 21 whereinthe step of determining object position data further comprises sensingthe maximum magnetic fields in each of a plurality of sensor planes. 25.The method according to claim 21 wherein the step of determining objectposition data further comprises using the magnetic field sensed in eachof four sensor planes.
 26. The method according to claim 21 wherein thestep of determining object position data further comprises using themagnetic field sensed in each of three sensor planes.
 27. The methodaccording to claim 21 wherein the step of determining object positiondata further comprises using the magnetic field sensed in each of twosensor planes.
 28. The method according to claim 21 wherein the step ofdetermining object position data further comprises using the magneticfield sensed in each of at least five sensor planes.
 29. The methodaccording to claim 21 wherein the step of determining object positiondata further comprises using the magnetic field value sensed in onesensor plane.
 30. The method according to claim 21 wherein the step ofdetermining capsule position data further comprises using the magneticfield sensed in one sensor plane wherein the maximum magnetic field isderived by partial differentiation of the magnetic field curve definedby the capsule, and wherein the capsule location is subsequently derivedusing the maximum magnetic field and nonlinear equations.
 31. An in vivoposition determination method comprising the steps of: placing a capsulecomprising a magnetic field in vivo; placing an external magnetic sensorarray for sensing the magnetic field of the capsule; and using thesensed magnetic field, determining capsule position data using magneticfield spatial geometry characterization point analysis.
 32. The in vivoposition determination method according to claim 31 comprising thefurther steps of; using an external magnetic sensor array for sensingbackground magnetic field presence; offsetting the capsule position datausing the sensed background magnetic field.
 33. The in vivo positiondetermination method according to claim 31 comprising the further stepsof; placing an external magnetic offset sensor for sensing backgroundmagnetic field presence; offsetting the capsule position data using thesensed background magnetic field.
 34. The in vivo position determinationmethod according to claim 31 wherein the step of determining capsuleposition data further comprises using the maximum magnetic field sensedin each of four sensor planes.
 35. The in vivo position determinationmethod according to claim 31 wherein the step of determining capsuleposition data further comprises using the maximum magnetic field valuesensed in each of three sensor planes.
 36. The in vivo positiondetermination method according to claim 31 wherein the step ofdetermining capsule position data further comprises using the maximummagnetic field value sensed in each of two sensor planes.
 37. The invivo position determination method according to claim 31 wherein thestep of determining capsule position data further comprises using themaximum magnetic field value sensed in each of at least five sensorplanes.
 38. The in vivo position determination method according to claim31 wherein the step of determining capsule position data furthercomprises using the maximum magnetic field value sensed in one sensorplane.